The present invention concerns a sports shoe or boot, notably for alpine skiing, ski touring, cross-country skiing, snowboarding, roller skating or ice skating, comprising a rigid frame arranged under the wearer""s ankle and defining at least a housing in which is placed an inner boot receiving the wearer""s foot and combining with this frame at least one link extension between the frame and one leg of the wearer, and at least one casing fitted to join the wearer""s leg firmly to the link extension.
The majority of sports shoes or boots such as shoes for in-line skates or skiing notably, comprise a rigid or hard shell stretching well above the ankle and gripping the latter so as to practically totally block its movements during sporting activities.
This type of shoe presents a certain number of disadvantages. Particularly due to their rigidity, the use of such shoes often causes injury such as notably:
diverse damage to knee and ankle ligaments;
painful tibia supports, posterior leg muscle affected;
bursitis on the foot, (Haglund""s disease);
inflammation of the Achilles tendon;
painful condition of internal and external ankle bones;
shin splints;
displacement and damage to the semilunar cartilage;
compression of the metatarsus (Morton""s syndrome);
stiffness of the lower member due to its compression;
atrophy of the foot muscles of the ankle and calf at the end of the season; and
cold feet, partial frostbite and associated circulatory complications.
Other sports shoes have been made with a hard shell which stops below the ankle and which is supposed to leave the ankle free. These shoes have the characteristic of blocking the foot in the shell by means of straps arranged on the instep.
The techniques employed in shoe and boot design have evolved to provide greater comfort, but this maintaining and locking action of the bottom of the leg still causes considerable injury and discomfort for wearers, often exposed to twisting of the bottom of the leg notably when falling. With hard shoes, the maximum resistance time of the twisting leg is considerably decreased by the rigidity of the shoes, which prevents complete movement of all the particular and muscular chain of the leg muscle segment. Violent twisting at the time of falling backwards is accentuated by the lack of posterior particular and muscular mobility of the leg, the effect of which is to transfer the twisting force abruptly onto the knees. The leg is blocked by the rigid neck of the shoe or boot. This type of fall widely described notably in the works of Professor Johnson in the United States shows up the dangers of ski boots that are too rigid, when falling and twisting backwards. On the other hand, it appears that blocking the feet and ankle articulations is responsible for the forced inactivity of leg muscles. These muscles are no longer correctly used to react in the case of a fall or unexpected change in direction and therefore do not correctly protect the knee and the ligaments. What is more, sensitivity of the foot is alleviated by this very same blocking of the foot and lower leg to which an external overall compression is added to obtain resistance and precision. The effect of this is to limit sensory activities. In the special case of skiing, this in part explains the difficulties of posture for many skiers.
Certain developments have been made to attempt to solve the problem of hard shell shoes or boots. One of these developments is illustrated in the U.S. Pat. No. 3,747,235. This document describes a ski boot comprising a rigid inner boot fixed to the ski and enveloping the foot, a lever fixed to the inner boot and extending practically up to the knee, a stirrup fixed to the lever and designed to prevent a sideways movement of the leg relative to the lever, and a strap which prevents longitudinal movement of the leg in relation to the lever. The rigid inner boot stops under the ankle and does not appear to block its movement. In actual fact, when the boot is held in a ski binding, the foot is blocked in the boot and the ankle articulation is blocked. The link between the leg and ankle is made by the lever that transmits the effort to the skis so as to allow the skier to direct the skis.
The aim of this boot is to avoid a certain number of problems associated with hard shell boots, in particular those due to compression of the foot in the shoe (bursitis, painful ankle bones, etc.). Unfortunately, this system does not allow using the muscular and particular locking of the whole leg. So, a certain number of problems persist and others appear.
The link between the leg and the ski is made just below the knee. This implies a risk of displacing and drawing of the knee. This xe2x80x9cdrawingxe2x80x9d is very frequent with those suffering from laxity or damage in knee ligaments. This can also cause inflammation of knee ligaments as well as compression of the glands and Thorel""s bundle. This link creates a compression and crushing of the posterior tibial artery, restricting irrigation of the lower leg. This strap is also directly against the fibula. It blocks the displacement of the latter which, during each leg movement, is normally displaced both in rotation and in translation.
The fact of blocking movements of the fibula causes pain and eliminates the natural particular and muscular blocking of the leg. Another problem associated with using a strap is the transmission of movement from the leg to the ski. If the strap is not very taut, this transmission is not perfect and the skis are difficult to direct. For transmission to be made in a reliable manner, it is essential that the leg cannot move at all in the strap. This implies that the strap must be very tight. It can result in pain of the same sort that appears with the use of hard shoes or boots.
Lastly, a major problem with this boot and its binding stems from the fact that the inner boot is firmly fixed in the binding. Although the ankle is not blocked by the boot itself, the rigid holding of the boot in the binding prevents natural movements of the foot, as is explained in detail below.
There are other documents describing sports shoes or boots designed to leave articulation of the ankle free. Among documents, the French patent applications published under No. FR-A-2 758 093 and FR-A-2 745 988 can be mentioned as well as the German publication No. DE 27 18 939.
The French patent application No. FR-A-2 758 093 describes an in-line roller skate formed by a conventional boot, a sole interdependent of the roller skates, a platform on which the boot rests, and a rigid extension linking the sole to the leg of the wearer. The rigid extension holds the leg through the use of a ring. This extension is mobile and can move forwards and backwards, but not sideways.
Given that the natural movement of the ankle implies also a sideways rotation during its forwards or backwards rotation, as the rotation axis of the ankle is not horizontal and perpendicular to the symmetrical line of the human body, the fact of stopping lateral rotation blocks rotation of the ankle at least partially. A chain displacement of leg articulations as a whole is therefore impossible, for one of the movements is blocked.
The German publication No. DE 27 18 939 describes a ski boot which can be used with a conventional inner boot. This boot comprises a shell in which the inner boot is immobilized by using air pads. The aim of this invention is to firmly maintain the foot in the shell, whilst avoiding restrictive zones. The fact of maintaining the foot stops natural movement of the leg.
Lastly, the French application No. FR-A-2 745 988 describes a sports shoe or boot comprising a rigid sole, a low drag-link which ends under the ankle and a guiding element which permits rotation of the tibia forwards, while at the same time preventing a sideways movement.
As is described in detail hereafter, all movement of the leg implies a coordinated movement of the ankle, knee and hip. The fact of preventing the movement of one of these articulations, even in one direction, destroys coordination of movement and prevents the leg from making a physiological displacement.
The sports shoes or boots of the prior art all have the same aim of maintaining the foot tightly, either in a hard shell, by straps on the instep or by inflatable pads, and a typical feature of preventing movement of the ankle in at least one direction.
Due to this, none of the inventions described in documents of the prior art allow a physiological movement of the leg in the sport involved, even in the case where articulation of the ankle appears to be free.
The present invention is offering to resolve the disadvantages of shoes or boots of the prior art by proposing a shoe or boot which allows the physiological movements of the leg as a whole, and of the ankle and knee in particular, notably by allowing movement of the sole of the foot as compared with the support made up by the ski or roller skate.
As mentioned previously, rotation of the leg as a whole can be divided into rotation of the knee, rotation of the ankle and rotation of the hip.
Rotation of the knee is controlled by two groups of muscles. The first group is made up of external rotator muscles which, when activated, have the effect of turning the tibial plate so as to direct the toes outwards. The second group includes internal rotator muscles which tend to direct the toes inwards. Overall, the group of internal rotators is slightly stronger than the group of external rotators. Bending the knee causes rotation of the tibia inwards as well as displacement of the fibula in rotation and translatory movement around its center line.
Rotation of the ankle can be made around three axes. One axis practically horizontal and transversal (X) which passes roughly by the ankle bones, a vertical axis (Y) situated in the extension of the leg and a longitudinal horizontal axis (Z).
The rotational movement of the ankle around the transversal horizontal axis (X) is called xe2x80x9cextensionxe2x80x9d when the toes are lowered, and xe2x80x9cflexionxe2x80x9d in the opposite case. The rotational movement around the vertical axis (Y) is called xe2x80x9cadductionxe2x80x9d when the toes are drawn inwards, towards the plane of symmetry of the body, and xe2x80x9cabductionxe2x80x9d when the toes are pushed outwards from this plane of symmetry. Lastly, movement around the longitudinal horizontal axis (Z) is called xe2x80x9csupinationxe2x80x9d when the sole of the foot turns inwards and xe2x80x9cpronationxe2x80x9d when it turns outwards.
During natural ankle rotation, movements around the three axes are always linked. Adduction is unavoidably accompanied by a supination and an extension.
The position reached is called inversion position. If the extension is compensated by an equivalent flexion, one obtains in varus stance.
In the other direction, abduction is accompanied unavoidably by pronation and flexion. The position reached is called xe2x80x9ceversionxe2x80x9d. If the flexion is cancelled by an equivalent extension of the ankle, one obtains ex valgus stance.
The xe2x80x9ceversionxe2x80x9d position is obtained mainly by the action of two musclesxe2x80x94the short lateral peroneal and the long lateral peroneal. These are attached to the front half of the sole of the foot, respectively on the outside edge and inside edge of the foot.
All the shoes or boots of the prior art maintain the foot tightly against the support. Furthermore, they prevent rotation of the ankle around the longitudinal horizontal axis (Z). Blocking of this movement breaks the particular chain formed by the ankle, knee and hip. This also has the effect of preventing the natural muscular blocking obtained by the physiological use of the muscles.
The aim of the present invention is to resolve the disadvantages of sports shoes or boots of the prior art and to allow a natural movement of the whole leg by allowing chain synergy of the leg articulations as described above. Another aim of the invention is to increase the sensitivity of the wearer. This aim is achieved by the fact that the lower member is free, therefore sensitive.
These aims are achieved by a sports shoe or boot such as is defined in the preamble and characterized in that the shoe or boot comprises means to allow a movement of the inner boot around a longitudinal center line of the foot in relation to the frame during use of the shoe or boot by the user and in that the link extension is resilient in flexion and in rotation.
According to a first embodiment, the means for allowing a movement of the inner boot around a center line can comprise at the least one longitudinal protuberance arranged between the inner boot and the frame, under the inner boot. The longitudinal protuberance can be interdependent of the liner or the frame.
According to a realization variant, the means to allow movement of the inner boot around a longitudinal axis comprises two longitudinal protuberances formed by a platform linked to the inner boot through a semi-rigid flat reinforcing rib in line with the said longitudinal axis.
This longitudinal protuberance disposed between the inner boot and the frame defines gaps on either side of this protuberance, these spaces being conveniently filled with soft stuffing matter.
The frame advantageously comprises means to allow a vertical movement of the back of the inner boot as compared to the frame. These means can comprise a shoulder arranged on the inner boot and a buffer stop shaped in the frame.
According to a preferred embodiment, the boot according to the invention comprises a back casing designed to be adapted to the morphology of the wearer""s calf, and a front casing designed to be adapted to the morphology of the wearer""s tibial plate, with at least one of the casings being linked to the link extension.
The front casing can comprise a support element for the knee, designed to be in contact with the wearer""s knee.
The casing fixed to the link extension is mobile in rotation over a given angular range around the said link extension and comprises adjustment means for volume between the back and front casing, and adjustment means for the height of the front casing and/or back casing.
According to a particular form of realization, one of the link extensions has an end element placed near to the extremity of the peroneal muscles.
One of the link extensions can also comprise an end element positioned near to the heel.
According to a particular embodiment, the boot comprises two link extensions.
In the first embodiment of the invention, one of the link extensions is arranged towards the back of the inner boot.
In a second embodiment of the invention, the two link extensions are arranged on the sides of the inner boot.
In a particular form of realization, the link extension is arranged between the inner boot and the frame.
The link extension can also be made up of at least two superimposed strips.
According to an advantageous variant, the inner boot is detachable from the frame.
According to a particular embodiment in which the shoe is used as a ski boot, the inner boots are preferably placed in the frames in such a way that when the skis are parallel, the edge of one inner boot, arranged towards the plane of symmetry of the wearer""s body, forms an angle opening forwards with the corresponding edge of the other inner boot.